Now to a promising but for some, controversial new medical procedure tonight. It uses your own stem cells to heal pain. Some say turning back the clock. But does the remedy come with a risk? Here's abc's tanya rivero tonight. Reporter: They're the injuries that come from pushing the body too hard and as we age, those bodies don't as quickly bounce back. Basically, people overdo it. Reporter:32-year-old eli says 12 years of weight lifting left him with crippling shoulder pain and nothing helped. Act cupunctacupuncture, massage, icing. Reporter: And eli is not alone. Every year, around 2 million, mostly middle aged americans, seek medical help for torn shoulder rotator cuffs. Around 100,000 undergo surgery on ripped knee ligaments. But then eli heard about a new half hour, non-evasive procedure that uses a patient's own stem cells to relieve the pain. Stem cells, or cellular therapy, as we call it, it's a strong anti-inflammatory. Reporter: The procedure is called a and here's how it works. Fluid is taken from the bone marrow of a patient's pelvis, spun for 15 minutes, separating the blood from the stem cells, which are then injected into the joint where the pain exists. Within two days, I was stronger than I had been in a dozen years. Reporter: But the fda and many doctors are still not convinced. Sometimes these stem cells can form tumors in certain areas. They can form tissues that are undesirable in certain areas. And we certainly don't want to take that risk. Reporter: Even though more doctors are beginning to offer the procedure off-label, it is still not approved by the fda, so, not widely available. Ny doctors caution that more testing needs to be done, but they acknowledge the future of stem cell therapy looks very promising indeed, david.

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